GSI attributes Chamoli flash floods to snow, ice, rock avalanche
Kolkata: Geological Survey of India (GSI) has attributed the flash flood that occurred in the Rishiganga and Dhauliganga valleys of Chamoli district, Uttarakhand on February 7 this year to a snow/ice/rock mass avalanche along with portion of jointed rockmass from the left valley wall of Raunthi Garh (a left bank tributary of Rishiganga River). More than 200 people were killed in the Chalmoli disaster and massive destruction was caused at two hydel power projects at Raini and Tapovan.
The dislodged rock/ice constituting from the avalanche crashed to the Raunthi Garh valley floor after travelling about 2,900 m with a vertical fall of around –1800 m. The energy of impact at a very high speed had pulverized the rock /snow/ice, besides generating melt water and the entire dislodged material of snow/ice/rock had rapidly flown in the downstream of Raunthi Garh and further down slope along the Rishiganga valley, causing this huge deluge and impacts to the elements-at-risks exposed across its path including formation of a temporary lake on Rishiganga River just immediately upstream of the confluence with Raunthi Gad.
According to Saibal Ghosh, Director GHRM (Geohazards Research and Management) Centre, GSI Central Headquarters, the second reason is due to the "Observed change in the hydro-meteorological conditions between 4th and 6th February, (heavy snowfall followed by sudden warmer climate) possibly triggered this huge snow and rock avalanche/ landslide causing sudden domino effect of flash flood in the downstream."
A GSI team that visited the spot to find out the causes leading to the disaster had found that though no appreciable damage was noticed further downstream of Joshimath, but the fury of the flash flood reached down to the Srinagar reservoir site in Rudraprayag district of Uttarakhand.
Interestingly, an artificial dam was formed near the confluence of Raunthi Garh and Rishiganga River, by the flowing debris which blocked the flow of Rishiganga River and formed a small lake temporarily posing another domino effect. Experts believe that high altitude areas of Himalayas are extremely hazard prone for disasters like Chamoli.
